Sustainable Energy Sources Essay -- Environmental Energy Solar Power E

Sustainable Energy Sources Energy is life. Life on this planet depends upon a fixed amount of energy. The modern industrialized energy sources such as coal and petroleum were originally utilized for their seeming promiscuity and high energies yielded per unit volume. The world has now become painfully aware of how finite petroleum reserves are, not to mention the political complications associated with being dependent upon foreign countries for an energy supply. To add insult to injury, the limitedness of petroleum resources is not the most pressing problem, their polluting byproducts are. The enormous amounts of byproduct waste that finds its way into our environment is having effects which even the most renowned of experts cannot determine in magnitude. Speaking from an economic standpoint, petroleum will soon become more expensive to find and utilize than reasonable alternatives, raising it’s costs far above it’s benefits. Some could already make the point that the social and environmental cos ts never were weighed appropriately into the cost/benefit analysis of petroleum and that the benefits associated with petroleum combustion have rarely or never outweighed it’s costs. This point will gain a painful clarity in the years to come if the predictions of some meteorologists come true and the effects of global warming are felt. For years developing societies have been taking enormous amounts of potential energy locked within pressurized biomass that took millions of years to store in the Earth’s crust and releasing it into today’s world. The Earth is a relatively closed system and the enormous release of spent energy and its polluting byproducts will have untold effects upon societies for generations to come. The most brazen ... ...echreview/www/articles/july95/Smith.html) Absorbers, Their Coating and Performance, The World Directory of RENEWABLE ENERGY Suppliers and Services, 1996 Solar Glass and It's Transmissivity The World Directory of RENEWABLE ENERGY Suppliers and Services, 1996 Overview of Solar Water Heating in the Caribbean, Griffin R. Carrison , REIA '94 Conference (http://www.solarenergy.net/tsen/database/griff.html) Institute of Space and Astronautical Science Solar Power Satellite Working Group, 1997 (http://www.reston.com/nasa/solar.sats.html) Chemistry 4th Edition, Steven S. Zumdahl, 1997, Houghton Mifflin Company, New York http://www.eren.doe.gov (U.S. Department of Energy) http://www.solarenergy.net/ (Solar Energy Network) http://www.hawaii.gov/dbedt/ert/ert_hmpg.html (State of Hawaii, Department of Business, Economic Development, and Tourism)

African American History Essay

Heritage makes up a large portion of our History. Combine that heritage with race and you have a foundation for establishing different beginnings of races that can trace their early origins back to the beginning of the United States. A giant melting pot as it has been described due to all of the immigration that occurred in the early nineteenth century. African Americans have established an enormous role in the beginnings and the history of the America. Their continuous fight for equality and rights as American people have spanned many years. The actions against African Americans immediately following the conclusion of the civil war were not fair. This initial unfair treatment sparked numerous debates that all can be followed back to their initial start of fair treatment after many years of mistreatment. The Black Codes were established to restrict and control the lives of ex-slaves. (Bowles 2011) That is not a way to be granted freedom if your life is still controlled. Freedom isn’t freedom if you are still treated unfairly amongst other races. The thirteenth amendment established to abolish slavery in the United States. This was a major step to equality among African Americans. The industrial boom in the north sparked the interest of many looking for work. The promise of a job and being able to provide for your family drew the attention of millions of African Americans. These jobs caused a mass movement of African Americans from the south to the north. This move was the Great Migration. The entry into World War Two brought some unique opportunities for African Americans. Key components to the war were the Tuskegee Airmen. Moving on in their fight for equal rights and treatments, Rosa Parks made a stand and refused to give up her seat on a bus. Seeing the need for more action by the government, Martin Luther king assembled a massive million man march into the Nation’s capital. The struggle for African Americans has been a long and at times dangerous struggle. Former slave owners and many others in the south did not wish to abandon their way of life and what they saw as fair and equal treatment for African Americans. With the determination, the will to make a difference, and legislative actions. African Americans have changed the laws and made remarkable steps towards the fair and equal treatment they were always entitled to as any American should be. Their nonstop pursuit of change has had an everlasting effect on history. The hopes and dreams of freedom for African Americans were destroyed immediately following the end of the civil war, because of black codes and the intimidation with terror and violence from veteran confederates that formed the terrorist group called the Ku Klux Klan. As newly freed slaves, blacks found out very soon that freedom was not how they dreamed. â€Å"In 1865, southerners created black code that controlled all aspects of black’s lives and stopped new found African Americans from the freedom that they had won from the civil war. † (The Black Codes of the South 1966) Almost every part of free slaves life was regulated by black codes even the freedom to migrate. Blacks could not enter certain towns without permission so hopes of finding family that were sold during slavery proved to be a challenge. There was also vagrancy laws that stated all freedman were vagrant if they did not have a job or they were homeless. Black codes made segregation in public facilities, carrying any kind of weapons, and to testify in court against white men illegal. If a black person disobeyed these codes and imprisonment would occur most of the time. This was a backwards step towards equality and freedom. Black codes did offer a few certain rights to blacks. They were given the right to marry, and the right to own some land. Although being a free black slave during this time period was a monumental step towards a unified country, blacks would face bigger challenges throughout the next century. The Thirteenth Amendment was one of the most influential amendments to have ever been passed in our country. The Thirteenth Amendment states, â€Å"Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction† (US Constitution, Amendment 13, Section 1) The intent of the Thirteenth amendment was to abolish slavery and begin the long process of just and equal rights for all American citizens. The passing of this amendment put an end to slavery and caused disruption to the former slave owners in the South. The Southern States that seceded from the union were forced to free their slaves and pass the amendment to be allowed back into the union. The south was then forced to find a new means of supporting themselves and working their cash crops. With this amendment passed, the African Americans were finally free and the vast majority of slaves the worked on plantations were gone because they were free. Although racism and segregation still played a major role in their lives, they were no longer forced to work as slaves. Slavery was not only a form of forced labor. Many slaves also faced humiliation, punishment, and harsh lives. They were some slaves that were treated as they were lower than they animals they were forced to care for. The origins of slavery and the continuation of slaves well into after the civil war were tarnish on America. The thirteen amendment abolished slavery, it did not offer much regulation onto gender equality. This was certainly true for former black female slaves. They were not afforded the same equal rights and opportunities as free former black male slaves. â€Å"Female slaves suffered unique hardships, being exploited for both labor and reproduction. † (Tsesis, A.2012). With the initial passing of the thirteenth amendment, the future road was being paved for equality amongst black both male and female. This amendment would go on to be ratified until eventually equality was achieved for both genders. The great migration covers the movement of millions of African Americans from the south to the north due to industrial expansion. Though this is not the first great migration, being there was a large migration of African Americans shortly after the civil war, this migration had a much larger effect. Populations of African Americans drastically changed because of it. Population diversity was established. During the 20th century, African- Americans participated in one of the most significant demographic events in U. S. history, â€Å"The Great Migration. † The Great Migration was a massive movement of African Americans from the South to the North spanning from 1863 to 1960. The largest movement in the migration occurred from 1910 to 1920. (Bowles 2011) The Great Migration was caused by different reasons that pushed African Americans out of the South, and other chances of opportunity were pulling them to the North. The spring on 1916, Six million African-Americans moved to the North and the West part of the United States of America. After the Emancipation Proclamation was signed in 1863, less than 8 percent of the African- Americans population lived in the Northeastern or Midwestern part of the United States. The U. S. Senate had ordered an investigation into it. In 1900, about 90 percent of blacks still lived in Southern states. They also moved to Canada in order to maintain safe haven from anti-abolitionists. When it was time for the blacks to move the only transportation for them were trains, boats, buses, but sometimes cars were used for their transportation. The promise of good employment, food, money, and a place to take care of your family drew the attention of many African Americans. The Great Migration created the first large urban black communities in the North. Along with massive amounts of blacks relocating to these cities also come problems. Many blacks were crammed into housing. At times, the occupancy of the housing that they lived in exceeded the limits they were designed for. Imagine an apartment that can accommodate five people comfortably being push over the limits by having twelve people reside in it instead. These were perfect conditions for disease, unsanitary conditions, and in some extreme cases, death. These dwellings became to be known as ghettos. All good things must come to an end and many blacks realized that due to the mass amount of laborers that migrated to the North, many of the jobs were taken. The south offered the work of the past, but this time they would be paid for it and not forced to do the work. â€Å"After the Great Migration, blacks continued to move in search of opportunity as some returned to the South, while others moved to suburbs or better neighborhoods within the North. †(Stewart E. Tolnay 2003) An important military milestone is African American history were the Tuskegee Airmen. These brave airmen were the first step towards race equality within the aviation sector of the military. Although African Americans had regularly fought in wars, they were not allowed to participate in actual aerial combat. The airmen were an import key in closing the race inequalities within the military. The Tuskegee airmen have become to be known as the most influential air squadron during world war two. Racism was still a major ongoing issue well into world war two. Many whites did not like the idea of African Americans being allowed to fly airplanes and fight in aerial combat. The Tuskegee Airmen did more than just that. They became the first black Army Air Corps pilots. Their beginnings started when President Roosevelt had arranged a meeting with three African American leaders of the Army and Navy. They argued that equality needed to be stable throughout the military, administration needed to be fair in regards to the ongoing draft, and African Americans should be allowed to fly. (Percy 2003) Shortly after the meeting had concluded, the War Department issued a policy directive stating that black men would be admitted into the military in numbers equal to civilian black population. In December of 1940, the Army Air Corps had submitted a plan that would establish experiments with a fighter squadron that consisted of all black pilots. Initially, thirteen black men were selected as pilot trainees for the program. The training occurred at Tuskegee Alabama, hence the name given, The Tuskegee Airmen. Majority of the instructors assigned to train the men were white. There were high hopes the failure would occur and this would prove to the War Department that African Americans were not suitable for flying. â€Å"The man probably most responsible for the success of the Tuskegee Airmen, the man whom the cadets looked to most often, was Captain Benjamin O. Davis Jr. (Percy 2003) Captain Davis helped keep the fight alive in all of the cadets which allowed them to ignore the Jim Crow laws that were still in place and they were able to focus their attention on becoming pilots. After the success of the Tuskegee Airmen, they became a vital part of the war effort. The Tuskegee Airmen were assigned combat missions, participating in aerial combat, and helping to win the war. The Tuskegee Airmen program was a giant step towards equality within the military and an important historical milestone in our history. A famous name associated with the Civil Rights movements is Rosa Parks. She was the average everyday woman. She rode the bus to and from work every day like any other ordinary person. She had acquired a job as a seamstress at a local department store in Montgomery Alabama. On the night of December 1, 1955, Rosa took the bus home as normal. The public bus was split into two different sections. There was a white section and a black section. If the white section filled up, people in the black section were required to give up their seat for the whites and they would have to stand. This was an unjust law in Montgomery that many blacks disagreed with. This did not seem like the equality that they deserved. Couple this law with all of the segregated services in Alabama; one would think that the hatred for free African Americans ran high. â€Å"Rosa refused to give up her seat despite the threats given to her by the bus driver. † (Wiltenburg, M 2001) She was arrested and forced to pay a fine of $14, which she never did end up paying. Word of her arrest spread fast and immediately following the next day, flyers emerged all around Alabama black schools and businesses pleading that those who rode the bus should seek alternate means of travel. The bus company was owned by whites even though majority of the passengers were black. The actions were to show that the law was not fair to blacks and hopefully the bus company would see this through their loss of profit due to their unfair rule. The boycott lasted well over a year. Finally the United States Supreme Court ruled that it was unlawful and illegal to treat people differently on the bus because of their skin color. (Wiltenburg, M 2001) The actions taken by Rosa Parks to generate a Civil Rights Movement were brave for her to conduct during the racist times of Montgomery. Her actions set off the initial movement that would pave the way for many more to come and challenge the racist laws that restricted the lives of black people. The Million Man March was another major event of the Civil Rights Movement. What better way to peacefully protest the unfair treatment of African Americans than to assemble in the Nation’s Capital and fight for equality among all races. Some Civil Rights Leaders were opposed to the march. Mary Frances Berry, Chair of the U. S. Civil Rights Commission, thought the actions of the march were â€Å"bad due to the black community being in deep trouble already. † (Winter, 1995-1996) Despite her disapproval, the march went on. While the actual number of participants can’t be pin pointed to an exact number, it is estimated that it was between 1. 5 and 2 million participants. This large showing of force allowed for peaceful protest and representation for the black community. They sought to gain the attention of the Federal Government so they could overcome the harsh reality that racism was still an ongoing issue and blacks were still being treated unequally by whites. Majority of the attendees were black males. The march was also attended by origins of race that were not primarily black. They saw an opportunity to take part in the possible change of equality and rights as well. Many famous black speakers were in attendance at the march, from Rosa Parks, Martin Luther King, and many black religious leaders. Although the peaceful protest eventually ended, it still remains one of the most talked about and biggest contributions to the Civil Rights Movements. History has shown that African Americans have faced a lot of challenges. Through unfair treatment in the early beginnings of America, African Americans were used as slaves and the country saw this as a normal and legal way of life. The actions taken by President Lincoln helped shed light on the tarnished actions of the American people and he is credited with having helped free the slaves. The black codes were a way that hateful southerners could still control the lives of black people. The southerners were upset because their way of life and what they saw as normal was being changed. The passing of the Thirteenth Amendment abolished slavery. This was a step in the right direction and it sparked the creation of many amendments to follow in suite. The great migration offered new hopes and promises of work in the North. Millions of African Americans began showing up in cities eager to get a piece of the American workforce. They were met with many housing, health, and physical challenges. Some blacks realized that the work in the North was not for them and they returned to the South to continue farming of their own free will and not under the control of slavery. World War Two brought light to African Americans with the chance of becoming pilots. The Tuskegee Airmen showed courage in the face of racism and overcame the discriminations brought onto them through the military. They became a vital part of the war effort and actively participated in aerial combat and bombing raids. Rosa Parks set the stepping stones for the Civil Rights movement. Her actions that night on the bus spread quickly and blacks refused to ride the buses in Montgomery Alabama. The efforts lasted well over a year and Congress finally determined that the law was unlawful. The million man march is one of the biggest actions in the Civil Rights movement. Blacks showed in large numbers to promote equality and diminish racism on the federal level. Many key speakers participated in this march, even though leaders of the Civil Rights Committee did not agree with the march. These actions taken by African Americans represent a small portion of the triumphs that they have overcome since slavery ended. There are many events and sacrifices that have been made by African Americans through the years. Their nonstop pursuit to end racism, have equality, and bring change to America will have an everlasting change on history. References Bowles, M. (2011). A history of the United States since 1865. San Diego, CA: Bridgepoint Education, Inc. Jim Crow and Uncle Sam: The Tuskegee Flying Units and the U. S. Army Air Forces in Europe during World War II William Alexander Percy The Journal of Military History , Vol. 67, No. 3 (Jul. , 2003), pp. 773-810 Published by: Society for Military History Article Stable URL: http://www. jstor. org/stable/3397326 Tuskegee: A Retrospect and Prospect Booker T. Washington The North American Review , Vol. 182, No. 593 (Apr. , 1906), pp. 513-523 Published by: University of Northern Iowa Article Stable URL: http://www. jstor. org/stable/25105549 Wiltenburg, M. (2001, Feb 20). The story behind the rosa parks story. The Christian Science Monitor. Retrieved from http://search. proquest. com/docview/405670133? accountid=32521 The Black Codes of the South by Theodore B. Wilson Review by: Irwin Unger The Florida Historical Quarterly , Vol. 45, No. 2 (Oct. , 1966), pp. 183-185 Published by: Florida Historical Society Article Stable URL: http://www. jstor. org/stable/30147751 Tsesis, A. (2012). GENDER DISCRIMINATION AND THE THIRTEENTH AMENDMENT. Columbia Law Review, 112(7), 1641-1695. Maloney, T. N. (2002). African American Migration to the North: New Evidence for the 1910s. Economic Inquiry, 40(1), 1-11. Annual Review of Sociology , Vol. 29, (2003), pp. 209-232 Published by: Annual Reviews Article Stable URL: http://www. jstor. org/stable/30036966 Marable, M. (1995). After the march. New Statesman & Society, 8(376), 14. How Black Academics Viewed the Million Man March The Journal of Blacks in Higher Education , No. 10 (Winter, 1995-1996), pp. 59-63 Published by: The JBHE Foundation, Inc Article Stable URL: http://www. jstor. org/stable/2962767.

The Dark Side of Application.ProcessMessages

Article submitted by Marcus Junglas When programming an event handler in Delphi (like the OnClick event of a TButton), there comes the time when your application needs to be busy for a while, e.g. the code needs to write a big file or compress some data. If you do that youll notice that your application seems to be locked. Your form cannot be moved anymore and the buttons are showing no sign of life. It seems to be crashed. The reason is that a Delpi application is single threaded. The code you are writing represents just a bunch of procedures which are called by Delphis main thread whenever an event occured. The rest of the time the main thread is handling system messages and other things like form and component handling functions. So, if you dont finish your event handling by doing some lengthy work, you will prevent the application to handle those messages. A common solution for such type of problems is to call Application.ProcessMessages. Application is a global object of the TApplication class. The Application.Processmessages handles all waiting messages like window movements, button clicks and so on. It is commonly used as a simple solution to keep your application working. Unfortunately the mechanism behind ProcessMessages has its own characteristics, which might cause big confusion! What does ProcessMessages? PprocessMessages handles all waiting system messages in the applications message queue. Windows uses messages to talk to all running applications. User interaction is brought to the form via messages and ProcessMessages handles them. If the mouse is going down on a TButton, for example, ProgressMessages does all what should happen on this event like the repaint of the button to a pressed state and, of course, a call to the OnClick() handling procedure if you assigned one. Thats the problem: any call to ProcessMessages might contain a recursive call to any event handler again. Heres an example: Use the following code for a buttons OnClick even handler (work). The for-statement simulates a long processing job with some calls to ProcessMessages every now and then. This is simplified for better readability: {in MyForm:}   Ã‚  WorkLevel : integer; {OnCreate:}   Ã‚  WorkLevel : 0; procedure TForm1.WorkBtnClick(Sender: TObject) ; var   Ã‚  cycle : integer; begin   Ã‚  inc(WorkLevel) ;   Ã‚  for cycle : 1 to 5 do   Ã‚  begin   Ã‚  Ã‚  Ã‚  Memo1.Lines.Add(- Work IntToStr(WorkLevel) , Cycle IntToStr(cycle) ;   Ã‚  Ã‚  Ã‚  Application.ProcessMessages;   Ã‚  Ã‚  Ã‚  sleep(1000) ; // or some other work   Ã‚  end;   Ã‚  Memo1.Lines.Add(Work IntToStr(WorkLevel) ended.) ;   Ã‚  dec(WorkLevel) ; end; WITHOUT ProcessMessages the following lines are written to the memo, if the Button was pressed TWICE in a short time: - Work 1, Cycle 1 - Work 1, Cycle 2 - Work 1, Cycle 3 - Work 1, Cycle 4 - Work 1, Cycle 5 Work 1 ended. - Work 1, Cycle 1 - Work 1, Cycle 2 - Work 1, Cycle 3 - Work 1, Cycle 4 - Work 1, Cycle 5 Work 1 ended. While the procedure is busy, the the form does not show any reaction, but the second click was put into the message queue by Windows. Right after the OnClick has finished it will be called again. INCLUDING ProcessMessages, the output might be very different: - Work 1, Cycle 1 - Work 1, Cycle 2 - Work 1, Cycle 3 - Work 2, Cycle 1 - Work 2, Cycle 2 - Work 2, Cycle 3 - Work 2, Cycle 4 - Work 2, Cycle 5 Work 2 ended. - Work 1, Cycle 4 - Work 1, Cycle 5 Work 1 ended. This time the form seems to be working again and accepts any user interaction. So the button is pressed half way during your first worker function AGAIN, which will be handled instantly. All incoming events are handled like any other function call. In theory, during every call to ProgressMessages ANY amount of clicks and user messages might happen in place. So be careful with your code! Different example (in simple pseudo-code!): procedure OnClickFileWrite() ; var myfile : TFileStream; begin   Ã‚  myfile : TFileStream.create(myOutput.txt) ;   Ã‚  try   Ã‚  Ã‚  Ã‚  while BytesReady 0 do   Ã‚  Ã‚  Ã‚  begin   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  myfile.Write(DataBlock) ;   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  dec(BytesReady,sizeof(DataBlock)) ;   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  DataBlock[2] : #13; {test line 1}   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Application.ProcessMessages;   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  DataBlock[2] : #13; {test line 2}   Ã‚  Ã‚  Ã‚  end;   Ã‚  finally   Ã‚  Ã‚  Ã‚  myfile.free;   Ã‚  end; end; This function writes a large amount of data and tries to unlock the application by using ProcessMessages each time a block of data is written. If the user clicks on the button again, the same code will be executed while the file is still being written to. So the file cannot be opened a 2nd time and the procedure fails. Maybe your application will do some error recovery like freeing the buffers. As a possible result Datablock will be freed and the first code will suddenly raise an Access Violation when it accesses it. In this case: test line 1 will work, test line 2 will crash. The better way: To make it easy you could set the whole Form enabled : false, which blocks all user input, but does NOT show this to the user (all Buttons are not grayed). A better way would be to set all buttons to disabled, but this might be complex if you want to keep one Cancel button for example. Also you need to go through all the components to disable them and when they are enabled again, you need to check if there should be some remaining in the disabled state. You could disable a container child controls when the Enabled property changes. As the class name TNotifyEvent suggests, it should only be used for short term reactions to the event. For time consuming code the best way is IMHO to put all the slow code into an own Thread. Regarding the problems with PrecessMessages and/or the enabling and disabling of components, the usage of a second thread seems to be not too complicated at all. Remember that even simple and fast lines of code might hang for seconds, e.g. opening a file on a disc drive might have to wait until the drive spin up has finished. It doesnt look very good if your application seem to crash because the drive is too slow. Thats it. The next time you add Application.ProcessMessages, think twice ;)